(a) Field of the Invention
This invention relates to a process for preparing cardiotonically active 3-substituted-2H-imidazo[4,5-b]pyridin-2-ones, to intermediate 2-substituted-amino-5-(pyridinyl)nicotinamides therefor and to the preparation and cardiotonic use of said intermediates.
(b) Description of the Prior Art
Lesher and Gruett U.S. Pat. No. 4,264,603, issued Apr. 28, 1981, shows the reaction of a 2-halo-5-(pyridinyl)nicotinonitrile with a hydrazine to produce 5-(pyridinyl)-1H-pyrazolo[3,4-b]pyridin-3-amines, which are useful as cardiotonics.
Lesher and Gruett U.S. Pat. No. 4,264,612, issued Apr. 28, 1981, shows lower-alkyl 2-halo-5-(pyridinyl)nicotinates and their use as intermediates for preparing 1,2-dihydro-5-(pyridinyl)-3H-pyrazolo[3,4-b]pyridin-3-ones and their use as cardiotonics, and also shows as intermediates 2-halo-5-(pyridinyl)nicotinoyl halides.
Baldwin et al [J. Med. Chem. 20, 1189-1193 (1977)] prepared 2-(3-pyridinyl)-1H-imidazo[4,5-b]pyridine and 2-(4-pyridinyl)-1H-imidazo[4,5-b]pyridine by heating respectively, a mixture of 2,3-diaminopyridine and nicotinic acid or a mixture of 2,3-diaminopyridine and isonicotinic acid. Both of these compounds were found by Baldwin et al to be inactive when tested as inhibitors of xanthine oxidase.